I did some S-AF testing with the E-M5 against (IIRC) a D800 and 5DIII and for S-AF there really wasn't much in it In my handful of very unscientific tests E-M5 was faster. Most of that comes down to the fact that the DSLR lenses are very fast, but if they have to go through a decent chunk of their focal range they have to move a fair bit of glass and mechanics (eg: cool moving rings while focussing). The M4/3s lenses focus groups seem to be able to pulse from end to end much faster.

I think it's inevitable that mirrorless will be able to focus faster and better than DSLR one day.